Unified Interior Regions

California

The Southwest Region includes California, Nevada, and Arizona. The Regional Office, headquartered in Sacramento, provides Center oversight and support, facilitates internal and external collaborations, and works to further USGS strategic science directions.

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Post-caldera eruptions of Mammoth Mountain, Dry Creek Dome, Earthqu...
August 2, 1998

Post-caldera eruptions of Mammoth Mountain (distant snow-covered pe...

View of Mammoth Mountain is toward the south-southwest. Dry Creek Dome and Deer Mountain are thick individual rhyolite flows (moat rhyolites) that were erupted about 115,000–97,000 years ago. Earthquake Dome consists of rhyo-dacite lava that is similar to the lava flows that built Mammoth Mountain; the dome was erupted about 86,000 ± 2 years ago.

Small red cinder cone perched on the west wall of Long Valley Calde...
August 2, 1998

Small red cinder cone perched on the west wall of Long Valley Calde...

The basaltic cone was erupted more than 64,000 years ago. The steep slope that cuts through the middle of the photo is the western caldera wall; the relatively flat ground in lower right is the west floor of the caldera. The layers of rocks exposed in the caldera wall above the cinder cone are among the oldest volcanic rocks in the area--they were erupted between 3.6 and 2

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Inyo Craters viewed from atop Mammoth Mountain toward the north with cartoon of magma supply below ground.
August 2, 1998

Inyo Craters magma supply cartoon.

Inyo Craters viewed from atop Mammoth Mountain toward the north with cartoon of magma supply below ground. The lower part of the diagram shows how the "dike" might appear if a square portion of the Earth's crust were removed along the axis of the Inyo vents.

Red Cones (lower left) viewed from atop Mammoth Mountain toward the...
August 2, 1998

Red Cones viewed from atop Mammoth Mountain toward the SW

The Red Cones are in lower left, and the valley in lower right is the Middle Fork of the San Joaquin River. Eruptions about 5,000 years ago built the two cinder cones and generated a small lava flow that spilled about 1.5 km (1 mi) down the valley wall.

Casa Diablo Hot Springs and the Mammoth geothermal power facility v...
July 30, 1998

Casa Diablo Hot Springs and Mammoth geothermal power facility

Mammoth Mountain is the dominant peak on the skyline, and the jagged peaks to the right of Mammoth Mountain are the Minarets. The Casa Diablo Hot springs are just beyond the power facility along the western edge of a down-faulted block at the southwestern margin of the resurgent dome. The low ridge in the middle right of the photo marks the western edge of the down-faulted

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Mammoth Lakes Basin including the treekill area next to Horseshoe L...
July 30, 1998

Mammoth Lakes Basin including the treekill area next to Horseshoe L...

The gray area along the edge of Horesehoe Lake (lower right) is one of several areas around Mammoth Mountain where trees were killed recently by high concentrations of carbon dioxide gas in the soil. Mary Lake (left of center) is the 2nd largest in the basin. The largest lake, Duck Lake, is accessible only by foot and is hidden from view.

South Inyo Crater with lake in crater.
July 29, 1998

South Inyo Crater.

View of the west wall of South Inyo Crater in the Mono-Inyo Chain, California. The rocky cliff visible in the crater wall is the top of a series of basaltic lava flows that were erupted between 200,000 and 100,000 years ago onto the west floor of Long Valley caldera.

Aerial view of the Inyo Craters with Obsidian Flow.
July 29, 1998

Aerial view of the Inyo Craters with Obsidian Flow in the foreground.

View of Obsidian flow is toward the north; Wilson Butte lava dome (mound in left center) and the lava flows and domes of the Mono Craters are visible behind Obsidian Flow, Mono-Inyo Chain, California.

South Deadman Flow...
July 29, 1998

South Deadman Flow.

This view of South Deadman flow (vegetation free area, left center) is from the northwest rim of Long Valley caldera looking toward the south. Mammoth Mountain is the snow-covered peak on right skyline.

Glass Creek and Obsidian Flow from atop Lookout Mountain, Long Vall...
July 29, 1998

Glass Creek and Obsidian Flow from Lookout Mountain, Long Valley CA

View in this photo is toward the west-northwest. The Glass Creek flow descends the northwest wall of Long Valley caldera. Highway 395 is visible through the tree

Resurgent dome in Long Valley caldera, viewed toward the east-south...
July 29, 1998

Resurgent dome in Long Valley caldera, viewed toward the east-SE fr...

The high point of the resurgent dome in the left center is Gilbert Peak. The west moat of the caldera forms the lowland in the foreground.

View of the northwest-facing slope of Mammoth Mountain....
July 29, 1998

View of the NW-facing slope of Mammoth Mountain.

View is from the northwest rim of Long Valley caldera looking toward the south. Mammoth Mountain is the broad snow-covered edifice built on the southwest rim of the caldera. This view across the forested west caldera floor (west moat) includes part of the South Deadman flow (lower left) and an unamed cinder cone (middle right). This andesitic cinder cone is breached on its

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USGS
August 8, 1997

The U.S. Geological Survey needs help to prepare for and assist at its big open house, September 12, 13 and 14, at the USGS Western Region Center in Menlo Park.

USGS
July 16, 1997

Experience over the last several years with the current system for describing the level of geologic unrest, such as earthquake swarms, ground deformation and gas emissions in the Long Valley caldera of eastern California, has shown it to be awkward and susceptible to misinterpretation by both the news media and the public.

USGS
July 8, 1997

A team of Bay Area earthquake scientists will be looking for more than old golf balls when they open an exploratory trench on the second fairway of the Mira Vista golf course in El Cerrito, this week. Golf course officials have rerouted the sedonc hole in order to give the geologists a 10-day window for the study.

USGS
May 29, 1997

Selected, local editions of U.S. Geological Survey topographic maps will be available for purchase at the USGS exhibit that will be part of the San Francisco Bay Trail Project’s National Trails Day Festival, Saturday, June 7, at Robert Crown Memorial State Beach and Crab Cove Visitor’s Center in Alameda.

USGS
April 15, 1997

Peat soils in the Sacramento-San Joaquin Delta and their relationship to water quality; the history and consequences of long-term groundwater use in the Mojave Desert; the hydrology, biology and geology of San Francisco Bay; 

USGS
April 15, 1997

Dr. Gordon Eaton, the national director of the U.S. Geological Survey in Reston, Va., will be one of the speakers at the Friday, April 18, 1997 dedication of Placer Hall on the California State University at Sacramento campus.

USGS
April 15, 1997

The presence of the U.S. Geological Survey in Placer Hall on the campus of California State University at Sacramento marks the latest chapter in the USGS’s long association with the study of earth sciences in California and cooperation with the state’s Division of Mines and Geology and its higher education system.

USGS
April 15, 1997

Methyl tert-butyl ether (MTBE) and its potential effects on air and water quality were the focus of a session Wed. and Thurs, April 16-17, 1997, at the American Chemical Society annual meeting in San Francisco, California. U.S. Geological Survey scientists will report on several studies of the occurrence and distribution of this compound in surface water and ground water during the session.

USGS
April 15, 1997

Methyl tert-butyl ether (MTBE) in the nation’s ground waters and surface waters will be the subject of papers and poster presentations by U.S. Geological Survey scientists at the American Chemical Society annual meeting, April 16-17, in San Francisco, Calif.

USGS
April 10, 1997

U.S. Geological Survey scientists are encouraged because they now know that they have the capability to explain the blind thrust faults of the Los Angeles region with seismic reflection methods, according to USGS researcher Dr. Rufus Catchings. 

USGS
March 17, 1997

A cooperative agreement with the University of Southern California (USC) for the operation of the Southern California Earthquake Center has been renewed by the U.S. Geological Survey.

USGS
February 18, 1997

LECTURE: -- "LIVING WITH GEOLOGIC HAZARDS IN SAN MATEO COUNTY" WILL BE THE SUBJECT OF THE NEXT U.S. GEOLOGICAL SURVEY’S FREE PUBLIC LECTURE.